Back to EveryPatent.com
United States Patent |
5,565,859
|
Matsumoto
|
October 15, 1996
|
Method of detecting a paging channel in a multi-frequency radio pager
network
Abstract
In order to detect a paging channel assigned to a pager in a shorter time
in a frequency divided pager network system, a plurality of paging
channels given priorities in channel searching are separately assigned to
the paging areas in a manner wherein reuse in adjacent paging areas is
avoided. A frequency subset number and frequency subset indicators related
thereto, are stored in a memory in a pager. Subsequently, paging channels
available in the system are allocated to the frequency subset indicators.
Further, a relationship between the frequency subset indicators and the
corresponding paging channels is arranged in the form of a table and then
stored in the pager. Then, the paging channels are assigned to the paging
areas according to the relationship. The above mentioned paging channels
given priorities in channel detection are monitored so as to detect which
priority channel is transmitted to the pager. In the event that the pager
detects one of the priority paging channels, the pager is tuned to other
paging channels according to the relationship.
Inventors:
|
Matsumoto; Mariko (Tokyo, JP)
|
Assignee:
|
NEC Corporation (JP)
|
Appl. No.:
|
373454 |
Filed:
|
January 17, 1995 |
Foreign Application Priority Data
Current U.S. Class: |
340/7.24; 340/7.42; 455/509; 455/515; 455/524 |
Intern'l Class: |
G02B 005/22; H04Q 007/00 |
Field of Search: |
340/825.44,825.48
379/59,60
455/33.2,33.3,33.4,34.2
|
References Cited
U.S. Patent Documents
4144412 | Mar., 1979 | Ito et al. | 455/33.
|
4747101 | May., 1988 | Akaiwa et al. | 379/59.
|
5058201 | Oct., 1991 | Ishii | 455/33.
|
5067147 | Nov., 1991 | Lee | 455/33.
|
5078905 | Feb., 1992 | Kuramatsu et al. | 340/825.
|
5254986 | Oct., 1993 | De Luca | 340/825.
|
Foreign Patent Documents |
8904025 | May., 1989 | WO.
| |
9003041 | Mar., 1990 | WO.
| |
9106190 | May., 1991 | WO.
| |
9107064 | May., 1991 | WO.
| |
Other References
Reports of the CCIR, 1990, Annex 1 to Volumn VIII pp. 12-18.
European Radio Message System (ERMES), pr ETS 300 133-4 Jan. 1991.
|
Primary Examiner: Horabik; Michael
Assistant Examiner: Merz; Edward
Attorney, Agent or Firm: Ostrolenk, Faber, Gerb & Soffen, LLP
Parent Case Text
This is a continuation of application Ser. No. 07/934,165 filed on Aug. 24,
1992, now abandoned.
Claims
What is claimed is:
1. A method of allocating pager channels to a plurality of paging areas in
a multi-channel radio pager network system wherein each pager is
previously assigned one frequency subset number (FSN) from among N defined
FSNs, and wherein N pager channels are available, each of said FSNs
defining M frequency subset indicators (FSIs), said FSIs being defined in
the form of a tree with M levels, said method comprising the steps of:
(a) selecting a plurality of priority paging channels from among said N
pager channels;
(b) allocating said plurality of priority paging channels to said plurality
of service areas on a one-to-one basis such that no priority paging
channel is assigned to two adjacent service areas;
(c) allocating the paging channels other than said priority paging channels
to said FSIs corresponding to each of said paging areas; and
(d) storing information in each of said pagers indicating the allocation of
the paging channels to said FSIs corresponding to each of said paging
areas.
2. A method as claimed in claim 1, wherein each of said pagers searches
said plurality of priority paging channels in an ascending order, in
preference to the paging channels other than said priority paging
channels.
3. A method as claimed in claim 1, wherein each of said pagers searches
said plurality of priority paging channels in an descending order, in
preference to the paging channels other than said priority paging
channels.
4. A method as claimed in claim 1, wherein if one of said pagers fails to
detect a paging channel, among said plurality of said priority channels,
through which messages are directed thereto, then said pager searches
another paging channel among the paging channels other than said plurality
of said priority paging channels by referring to said information.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of detecting a paging channel in
a multifrequency radio pager network wherein an overall service coverage
area is divided into a plurality of small paging areas. More specifically,
the present invention relates to such a method wherein the paging channel
to be detected is dynamically assigned to one of a plurality of frequency
subset indicators in a given paging area. The frequency subset indicators
are related to one frequency subset number.
2. Description of the Prior Art
It is known in the art that a radio pager is a device which alerts a
subscriber to call a predetermined phone number by means of sound and/or
flashing light.
Recently, in order to transmit more pieces of information to a subscriber
at one calling, a radio pager which is equipped with a display function,
has proven very popular and is gradually replacing the above mentioned
older style pagers.
A radio paging system currently in use is designed such that a pager is
able to receive its paging messages, via a predetermined paging channel,
throughout an entire service coverage area to which the subscriber has
subscribed. In other words, there exists no radio pager system wherein a
service coverage area is divided into a plurality of small paging areas
and wherein a pager uses different frequencies in different paging areas.
However, merely by way of example, the European Telecommunications
Standards Institute has proposed to provide frequency divided network
operations in the European Radio Message System (ERMES). The frequency
divided network operation implies that adjacent paging areas use different
frequencies. Within one network a pager should use adjacent frequencies in
adjacent paging areas.
In the frequency divided (viz., multifrequency) network, each of the pagers
is informed on which channel to expect its messages. This is accomplished
with a combination of a frequency subset indicator (FSI) transmitted to
all pagers in a system information partition and a frequency subset number
(FSN) permanently stored in the pager. The frequency subset indicator
(FMI) shall be transmitted for all pagers.
FIG. 1 is a chart which depicts a format of the paging signal which is
transmitted to the pagers in the ERMES. The code format Shown in FIG. 1
starts with a synchronization part which consists of a preamble word (PR)
and a synchronization word (SYN). A system information partition comes
next which consists of two system information (SI, SI') parts and a
supplementary system information (SSI) part. The system information
partition is followed by address and message partitions as shown.
FIG. 2 is a diagram which illustrates a relationship between frequency
subset indicators (FSIs: 30-00) and frequency subset numbers (FMNs:
00-15), both of which have been proposed by the above mentioned ERMES.
Each of all pagers shall be assigned a single FSN between 00 and 15. Each
FSN defines a unique subset of five FSIs as indicated in FIG. 2. It is
intended that the FSIs are used in descending order. Thus, in the event
that a single channel is used within a paging area, the transmitted FSI is
set to 30. On the other hand, if two channels are used within a paging
area, the transmitted FSIs are set to 28 and 29. The FSI(s) transmitted is
located in the system information SI' in the code format of FIG. 1.
It is assumed that the number of frequency channels assigned to an overall
service coverage area is 16 and depicted by F0-F15. It should be noted
that the FSIs do not correspond directly to frequency channel numbers. In
more specific terms, a system operator allocates one or more of the 16
channels F0-F15 to one or more of the thirty FSIs (viz., FSI values of 31
to 00) in each paging area. Thus, the FSI/FSN arrangement renders it
possible to have a dynamic number of channels in use.
The FSI broadcast on the paging channel indicates that messages wall be
transmitted for pagers with an FSN in the FSI's subset. For example, when
the FSI on a channel equals 27, only messages to pagers with FSNS 12, 13,
14 and 15 will be carried. Conversely, a pager with FSN=12 should look for
its messages, only on one of the channels broadcasting FSI values of 12,
22, 27, 29 or 30.
Merely for the convenience of description it is assumed that:
(a) the pager with FSN=12 enters a given paging area;
(b) the pager has previously stored FSI values of 12, 22, 27, 29 and 30 in
a memory it is equipped with; and
(c) four frequency channels F15, F10, F8 and F2 are used in the paging area
in question and assigned respectively to the FSIs of 27, 26, 25 and 24 as
indicated in FIG. 2.
With these assumptions, the pager with FSN=12 has to detect channel F15
which has been assigned to FSI=27, one of its five FSIs, and then fix
itself one channel F15. In this end, the pager begins to search for the
channel F15 by sequentially changing the tuning frequencies in a
predetermined order using a frequency synthesizer it is equipped with. It
is further assumed that the channel searching is implemented in an
ascending order (viz., from F0 to F15) by way of example.
The pager is firstly tuned to the frequency F0. Since F0 is not in use in
this particular case, the pager tuning proceeds to the next frequency F1
which is also not in use in this case. Following this, the pager is tuned
to F2. However, the FSI value of 24 transmitted on the channel F2 has not
been assigned to the pager in question and accordingly, the pager is
subsequently tuned to the following channel frequencies (viz., from F02 to
F15).
When the pager is eventually tuned to the channel F15, it detects the
FSI=27 in the system information partition (FIG. 1) on the channel F15 and
is fixed to same and awaits the forthcoming message reception.
The above mentioned prior art techniques have suffered from the difficulty
in that the number of channel tuning operations is apt to be undesirably
large before the assigned channel is detected, and in the worst case is
carried out 16 times.
This problem is especially disagreeable in the case where a pager
subscriber frequently moves from one paging area to another.
FIG. 3 schematically illustrates such a case wherein a service coverage
area is divided into 6 paging areas A1-A6 by way of example. It is assumed
that the paging areas A1-A6 have been assigned the frequency channels F0,
F2-F4, F7-F8, F10-12 and F14-F15 as indicated. If a given pager moves from
a point M to N along a broken line, the pager is required to search for
the channel assigned thereto every time it enters the adjacent areas. As
mentioned above, the pager is unconditionally, successively tuned to the
channels in a predetermined order and, accordingly the tuning operations
are time consuming.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method by which a
frequency channel assigned to a pager can be found in a shorter time.
In brief, the above object is achieved by a method wherein in order to
detect a paging channel assigned to a pager in a shorter time in a
frequency divided pager network system, a plurality of paging channels
which are given priorities in channel searching are separately assigned to
the paging areas in a manner wherein reuse among adjacent areas is
avoided. A frequency subset number and frequency subset indicators related
thereto, are stored in a pager. Subsequently, paging channels available in
the system ere allocated to the frequency subset indicators. Further, a
relationship between the frequency subset indicators and the corresponding
paging channels is arranged in the form of a table and then stored in the
pager. Then, the paging channels ere assigned to the paging areas
according to the stored relationship. The above mentioned paging channels
given priorities in channel detection are monitored and are transmitted to
the pager. In the event that the pager detects one of the paging channels
with priorities, the pager is tuned to other paging channels according to
the stored relationship.
More specifically an aspect of the present invention is concerned with a
frequency divided pager network system whose service coverage area is
divided into a plurality of paging areas. A paging channel is separately
determined for each of the paging areas in connection with each of pagers.
Each pager being previously assigned to one of a plurality of frequency
subset numbers. Each paging channel is assigned to one of a plurality of
frequency subset indicators which are related to the frequency subset
numbers.
A method embodying the present invention comprises the steps of: (a)
determining a plurality of first paging channels which are separately
assigned to the paging areas in a manner wherein reuse in adjacent areas
is avoided; (b) storing a frequency subset number and frequency subset
indicators related thereto in a pager; (c) assigning paging channels
available in the system to the frequency subset indicators and arranging a
relationship between the frequency subset indicators and the corresponding
paging channels in the form of a table; (d) allocating the paging channels
to the paging areas according to the stored relationship; (e) monitoring
for the first paging channels transmitted to the pager; and (f) tuning the
pager to paging channels according to the relationship in the event that
the pager detects one of the first paging channels.
BRIEF DESCRIPTION OF THE DRAWINGS
The features and advantages of the present invention will become more
clearly appreciated from the following description taken in conjunction
with the accompanying drawings in which like elements are denoted by like
reference numerals and in which:
FIG. 1 is a chart depicting a known format of the signals which are applied
to a pager, this figure being applicable to the prior art and also being
useful for explaining the present invention end having been referred to in
the opening paragraphs of the instant disclosure;
FIG. 2 shows an FSI/FSN relationship in a known paging system which has
been discussed in the opening paragraphs of the instant disclosure;
FIG. 3 is an illustration depicting the movement of a subscriber in and out
of a number of different paging areas in the known paging system;
FIG. 4 is a block diagram showing a pager to which the present invention is
applicable;
FIGS. 5 to 10 show a FSI/channels relationship for illustrating the present
invention;
FIG. 11 is an illustration depicting an allocation of paging channels in
paging areas according to an example of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to FIG. 4, there is shown in block diagram form a hardware
arrangement of a pager 10 to which the present invention is applicable.
It is assumed that the pager 10 has not yet been tuned to the channel which
has been assigned thereto. It is necessary, therefore, to ascertain the
channel for enabling the pager 10 to receive paging messages directed
thereto. This operation is required in the event that the pager 10 is
initially energized due to the replacement of a battery or if the pager 10
is transported into an adjacent paging area, etc.
As shown in FIG. 4, a front end (viz., radio section) 12 is provided for
amplifying and demodulating a code-modulated carrier wave (viz., channel
frequency) received by an antenna 14. The front end 12 comprises a high
frequency amplifier, a frequency converter, an IF amplifier and a
discriminator (not illustrated in FIG. 4). The front end 12 is tuned to
one of the above mentioned channels F0-F15 (for example) under control of
a frequency synthesizer 13 and a controller (viz., CPU (Central Processing
Unit)) 22. In the event that the front end 12 is successfully tuned to an
incoming carrier wave, the output of the front end 12 is applied to a
decoder 16. Otherwise, the controller 22 instructs the front end 12 to
proceed to the next channel frequency using the synthesizer 13. These
operations are repeated until the front end 12 is successfully tuned to
the incoming channel frequency.
The decoder 16 is arranged to compare an FSI transmitted on the "tuned"
channel with one of the FSIs which have previously been assigned to the
pager 10 and stored in a memory 18. The FSI transmitted is located in the
section SI' of the system information partition (FIG. 1). The FSIs in the
memory 18 are written thereinto from a non-volatile memory 20 when the
pager 10 is switched on. The FSIs stored in the pager 10 will be referred
to in more detail later.
If the decoder 16 fails to detect that the FSI transmitted on the "tuned"
channel coincides with one of the FSIs previously stored in the memory 18,
the controller 22 instructs the front end 12 to tune to the next channel
using the synthesizer 13.
On the other hand, if the decoder 15 detects that the received FSI on the
"tuned" channel coincides with one of the FSIs stored in the pager 10, the
controller 22 fixes the tuning frequency (viz., channel) at the front end
12 and thus terminates the channel search operations. Following this, the
pager 10 enters into a standby mode for receiving any paging messages
directed thereto within the paging area wherein the pager 10 has
ascertained that the received FSI on the "tuned" channel coincides with
one of the FSIs stored in the pager 10.
After the pager 10 has entered into the standby mode, when it receives a
signal transmitted over the paging channel which has been fixed by the
above mentioned operations, the decoder 16 proceeds to compare an incoming
pager address code with a pager ID (Identification) code stored in the
memory 18. The pager ID code in the memory 18 is written therein from a
non-volatile memory 20 when the pager 10 is switched on.
In the event that the incoming pager address code coincides with the pager
ID code, the decoder 16 applies a message signal, which follows the
coincident pager address code, to the controller 22.
Subsequently, the controller 22 energizes a speaker 24 by way of a speaker
driver 36. Although not shown in FIG. 4, a light source such as an LED
(Light Emitting Diode) or the like, may be installed to provide a visible
signal in addition to the audible one produced by the speaker 24. Further,
the controller 22 stores the message in a RAM (Random Access Memory) 28
and simultaneously induces the same to appear on a display 30 using a
display controller 32 in a manner known in the art.
The controller 22 is arranged to control the overall operations of the
pager 10 using a program which is previously stored in a ROM 34.
The present invention will be discussed in more detail with reference to
FIGS. 5-11.
As mentioned in the opening paragraphs of the instant specification, all
pagers are assigned an FSN between 0 and 15. Further, each FSN defines a
unique subset of five FSIs as discussed above in connection with FIG. 2.
It is assumed that the service coverage area of a multi-channel pager
network is divided into six paging areas A1-A6 as shown schematically in
FIG. 11. According to one embodiment of the present invention, each of the
FSIs 00-03 and 14-30 is assigned a paging channel in each of the paging
areas A1-A6 as shown in FIGS. 5-10, respectively. The relationship of each
of the FSIs and the corresponding paging channels shown in FIGS. 5-10, is
previously stored, in the form of a look-up table, in the non-volatile
memory 20 of each pager (FIG. 4). Further, the paging channels F0-F5 are
separately assigned to the paging areas A1-A6 in a manner wherein none of
the paging channels F0-F5 is assigned to two adjacent paging areas. The
paging channels F0-F5 are defined to be main or priority channels which
are first searched by each pager in order to determine a paging channel
through which a message will be transmitted to that pager.
When the pager 10 is required, in one of the paging areas A1-A6, to
ascertain the paging channel through which paging messages directed to the
pager 10 is received, the pager 10 will be sequentially tuned to the
channels F0-F5 in an ascending, descending or suitably determined order.
Since each paging area A1-A6 is assigned to one of the channels F0-F5, the
pager is eventually tuned to one of the channels F0-F5 after at most five
channel searches.
It is assumed in this example that the pager with the FSN=12 initiates the
channel search while located in the paging area A1 to which the main or
priority channel F0 has been allocated (FIG. 11). If the pager 10 is
sequentially tuned to the priority channels F0-F5 in an ascending order
the pager 10 is first tuned to the channel F0. Then the controller 22
accesses the corresponding look-up table (viz., FIG. 5) in the memory 20.
In this instance although, F0 is in use as shown in FIG. 11, the pager 10
with the FSN=12 fails to detect coincidence between the transmitted FSI=28
and any of the stored FSIs=30, 29, 27 and 22. Accordingly, the controller
22 of the pager 10 accesses a look-up table which has been stored in the
memory 20 and which indicates the FSI/channel relationship shown in FIG.
5. This occurs because the pager 10 has already acknowledged that it is
located in the paging area after being successfully tuned to the paging
channel F0. Therefore, the front end 12 is directly tuned to the channel
F11 in the next step in this particular case. Thus, the pager 10 detects
the coincidence of the FSI=29 transmitted over the channel F11 with the
FSI=29 stored in the pager. This means that the pager 10 is able to
ascertain F11 as the channel assigned thereto. Subsequently, the pager 10
enters into a message waiting mode.
It is noted in FIG. 5 that a pager grouped into the FSN=00 is only tunable
to the channel F0. Conversely, a pager related to the FSN=15 can be tuned
to one of the five channels FO, F11, F13, F14 and F15.
The above discussions are applicable to other pagers with FSNs other than
FSN=12 and also to the other paging areas A2-A6 to which main or priority
channels F1-F5 are assigned respectively.
In the foregoing, the so-called priority channels which ere firstly
searched for, are by no means limited to F0-F5 and also the number thereof
is not limited to six. Further, the relationships between the FSIs and the
channels corresponding thereto, shown in FIGS. 5-10, are merely exemplary
and not restricted thereto, That is to say, the FSI/channel relationship
can be altered to comply with situations which require modifications.
It will be understood that the above disclosure is representative of only
one possible embodiment of the present invention and that the concept on
which the invention is based is not specifically limited thereto.
Top